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Effectiveness of typhoid conjugate vaccine against culture-confirmed typhoid in a peri-urban setting in Karachi: A
Rabab Batool1, Mohammad Tahir Yousafzai2, Sonia Qureshi3
1Department of Pediatrics and Child Health, Aga Khan University Hospital, National Stadium Rd, Aga Khan University Hospital, Karachi City, Sindh 74800, Pakistan; Adolescent, and Maternal Health, Faculty of Medicine and Health Technology, Tampere University, Kalevantie 4, 33100 Tampere, Finland.
Insights
Typhoid Conjugate Vaccines (TCV) show 72% effectiveness against Salmonella Typhi in children aged 6 months to 15 years. This study in Karachi, Pakistan, highlights TCV
Area of Science:
- Vaccinology
- Infectious Diseases
- Public Health
Background:
- Enteric fever, caused by Salmonella Typhi and S. Paratyphi, poses a significant health burden in South Asia, particularly among children.
- Increasing antimicrobial resistance complicates treatment and control of typhoid fever.
- World Health Organization recommends Typhoid Conjugate Vaccines (TCV) for individuals aged 6 months to 45 years in endemic areas.
Purpose of the Study:
- To evaluate the effectiveness of TCV against culture-confirmed Salmonella Typhi infections.
- To assess TCV's impact in a high-burden, extensively drug-resistant (XDR) typhoid outbreak setting in Karachi, Pakistan.
Main Methods:
- A matched case-control study was conducted in Lyari Town, Karachi, Pakistan.
- Cases were children aged 6 months to 15 years with culture-confirmed S. Typhi.
- Controls included age-matched hospital and community participants.
Main Results:
- Vaccine effectiveness of a single TCV dose was 72% (95% CI: 34%–88%).
- Consumption of outside meals more than once monthly was linked to increased typhoid risk (aOR: 3.72, 95% CI: 1.55–8.94).
Conclusions:
- A single dose of TCV is effective in preventing culture-confirmed typhoid.
- TCV demonstrates significant protection in children during an XDR typhoid outbreak in a peri-urban Pakistani community.
Background:
Enteric fever, caused by Salmonella Typhi and S. Paratyphi, is a cause of high morbidity and mortality among children in South Asia. Rising antimicrobial resistance presents an additional challenge. Typhoid Conjugate Vaccines (TCV) are recommended by the World Health Organization for use among people 6 months to 45 years old living in endemic settings. This study aimed to assess the effectiveness of TCV against culture-confirmed S. Typhi in Lyari Town, Karachi, Pakistan. This peri-urban town was one of the worst affected by the outbreak of extensively drug resistant (XDR) typhoid that started in November 2016.
Methods:
A matched case-control study was conducted following a mass immunization campaign with TCV at three key hospitals in Lyari Town Karachi, Pakistan. Children aged 6 months to 15 years presenting with culture-confirmed S. Typhi were enrolled as cases. For each case, at least 1 age-matched hospital control and two age-matched community controls were enrolled. Adjusted odds ratios with 95% confidence intervals (CIs) were calculated using conditional logistic regression.
Results:
Of 82 typhoid fever patients enrolled from August 2019 through December 2019, 8 (9·8%) had received vaccine for typhoid. Of the 164 community controls and 82 hospital controls enrolled, 38 (23·2%) community controls and 27 (32·9%) hospital controls were vaccinated for typhoid. The age and sex-adjusted vaccine effectiveness was found to be 72% (95% CI: 34% - 88%). The consumption of meals prepared outside home more than once per month (adjusted odds ratio: 3·72, 95% CI: 1·55- 8·94; p-value: 0·003) was associated with the development of culture-confirmed typhoid.
Conclusion:
A single dose of TCV is effective against culture confirmed typhoid among children aged 6 months to 15 years old in an XDR typhoid outbreak setting of a peri-urban community in Karachi, Pakistan.
